Constructing a stable interface film on both cathode and anode via a novel electrolyte additive for high performance LiNi0.8Co0.1Mn0.1O2/graphite pouch cell

LiNi0.8Co0.1Mn0.1O2 (NCM811)/graphite battery is extensively concerned due to its high specific energy and low-cost. However, the unstable cathode/solid electrolyte interface (CEI/SEI) in carbonate-based electrolyte limits its development, especially under high voltage and high temperature. Herein, a novel electrolyte with 3-cyano-2,5,6-trifluoronicotinonitrile (CTFP) as an additive is proposed to construct a highly stable interface film on both cathode and anode to improve the electrochemical performance of NCM811/graphite battery. The experimental characterizations and theoretical calculations demonstrate that CTFP can preferentially catch PF6− on the NCM811 surface and then be oxidized to generate a N-containing polymer which can strongly absorb PF5 and inhibit the formation of HF and the dissolution of transition metal (TM) ions on the cathode, and meanwhile, it is reduced to form a LiF-rich SEI on the anode. As a result, by adding 0.5 wt% CTFP into the basic electrolyte, the capacity retention of commercial NCM811/graphite pouch cell with 1800 mAh can be enhanced from 48 % to 75 % at 1 C after 200 cycles between 3.0 V and 4.35 V at 25 °C and the capacity retention of NCM811/graphite pouch cell with 16 mAh is improved from 46 % to 69 % at 1 C after 300 cycles between 3.0 V and 4.25 V at 55 °C. This new additive provides a universal strategy to establish a highly stable interface film on both NCM811 and graphite for high performance lithium-ion batteries.